Amplifying system



D60. 1, 1931. TAYLOR 1,834,229

AMPLIFYING SYSTEM Filed Nov. 7, 1927 INVENTOR.

ATTORNEY Patented Dec. 1, 1931 UNITED STATES PATENT OFFICE ALBERT H. TAYLOR, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB, BY MESNE ASSIGNMENTS, T FEDERAL- TELEGRAPH COMPANY, A CORPORATION OF CALI- FORNIA AMPLIIYING SYSTEM Application filed November 7, 1927. Serial No. 231,591.

"Another object of my invention is to provide a balanced high frequency system for high power amplification wherein inter-grid and inter-plate oscillations are prevented.

Other objects of my inventionreside in the amplifier circuit arrangements described in the specification hereinafter followingby reference to the accompanying drawings in which:

Figure 1 shows the circuit arrangement of my invention as applied tothecoupling system between adjacent stages of a high frequency power amplifier system; Fig. 2 isa modified balanced amplifier circuit arranged according to my invention; and Fig. 3 is a further modified form of the circuit of my invention.

Fig. 1 shows at the left' a tube 1 whose platecircuit is provided with modified series tun ing according to my invention for. coupling with the circuits of tube .2." The diagram' shows two tubes arranged in cascade but it will be understood that a multiplicity of tubes can be operatedin parallel provided the usual precautions are taken to prevent inter-grid and Y inter-plate frequency oscillations from occurring. The condenser-3 is a stopping condenser of relatively large ca? pacity, and in the circuits herein described can be neglected as far as its influence onthe tain distinct advantages, although it necessi-r tates a particular method of exciting the grid of the succeeding tube 2 shown on the ancing or neutralizing between thetwo tubes.

tuning of the circuit is concerned. The con right of Fig. 1 and aparticular method of bal- An analysis of the electromotive forces in the" circuit will make this clear. If the radio frequency current through the condenser 5 and coil system 6 is assumed as the basis of phase and the filaments 1a and 2a considered to be at ground potential 111,, it will be seen that the voltage E across the condenser 5 is 90 bei hind the current and is inversely proportional at a given frequency to the value ofthe capacity 5. On the other hand, the voltage across that portion of the coil system 6 in active use, which has been split into two parts E and E is 90 ahead of the current, and therefore in opposition to the voltage E The voltage E is equal to the vector sum of the voltages E E and E,. On account of the opposition between the voltage E and the voltages E and E there will besome point on the coil system 6 which will be a node, and

which will therefore, also have the potential E At this point E becomes equal and opposite to E To get the necessary exciting voltage on the grid of the amplifier tube which follows the tube 2 on the left, whose circuits we are discussing, it is therefore necessary, contrary to usual practice, to bring the excitation tap well up to the top ofthe coil system as shown at 10 in Fi re 1. There is an alternative, but this will be discussed later in connection with Figure 2; This node can actually be found by the use of a Neon tube or voltmeter and the distri-'' bution of potential in the coil system is found to be exactly as described. Now, in order to balance this tube against the tube which follows it, it is necessary to connect the plate 2b of thesucceeding tube through a balance condenser 7 and connection 9 to some point whose potential is opposite in phase to the potential supplied to the grid, and having a suitable value. Such a point will be found on the portion of the coil system below the nodal point E All points below E have a poten-- tial opposite in phase to that of the grid 'potential of the following tube 2, but to get the right amount of balancing potential it may, in some cases,be necessary to extend the coil 6 as shown'in Fig. 1, so that the balancing tap may be brought. on to turns which are below the point where'the condenser 5 is connected to the coil system. The manner of exciting the grid of the following tube 2 requires the.

tap to be put well up into the coil system 6.

Fig. 2 shows an alternative method of ex- 5 citing the grid 20 and balancing it, which for some high power high frequency-circuits has advantages. Here the voltageiE -is used;

for excitation purposes to the grid of the following tube 2, the circuit connection being 10 adjacentoneendof theinductance 6. A-sim I ilar analysis of the voltagesin the systemholds for this circuit, from which it is clear that the balance tap must be put above -the nodal point E The connection 9 including condenser 7 extends from pl'ate'2'b'to a point on coil 6 above thenodal point.

Fig.,. 3 shows avariation of..the method of 2 wherein the condenser 5 is replaced by two condensers in series at 11 and 12, the excitation tap 10 for the grid 20 ofthe following, tube 2 being placed attheir junction at 14.. By:shifting'theva lues of Hand 12 moreror less voltage may be directed onto the; grid 20 of the followings tube 2. ,Thisis a i capacity potentiometer which gives control of .excitationon the grid 20 of the following tube 2 without having to shift taps in the coil system 6. Hereagain it is necessary to put the-balance tap 9 connectingthe plate of the following tube atapoint abovethe nodal point E Condenser C is an" impedance.

condenser, that is, it serves thepurpose of-adjusting the external and internal impedances ofthe tube forbest efficiency. It should be understood also that the coil system6 itself is capablenof variation so that a suitable amount-ofinductance can be put in not only totunein properly thedesired frequency supplied to the grid of the left-hand-tube 2 but ;"to tuneitinin such a way as to give a good efficiency- Itis .to be understood that these circuits. are particularly valuable at high:

frequencies and at highpower. p I g The .capacitativereactances constituted by the: condensers 11 and 12 are simultaneously adjustable for varyingthe grid excitation and locating and positioning thenode ofthe current in theoutput circuit intermediate the ends of theinductance 6' forsecuringthe desired balanced operation of the amplificationcircuits; V b

The circuit arrangement of myinvention has. beenfound to be very desirable for high power longdistant radio telegraphic signal ing on short waves. p

While I have :described preferredembodn ments of my invention, I desire that itbeunderstood-that modifications may be made and j that no limitations are intended other Ethan are imposed by, the scope of the appended claims.v V

Wliat I :claim as new bytLetters Patent ofthe-Uiiitedstates is as follows;

--power.amplification for and desire to secure in saidoutput circuit intermediate the ends of-said inductance and a connectionbetween said capacitative reactances to the 'gridelectrodeof the succeeding electron tube for effecting excitation of the succeeding tube from a position belowth'e nodal point of said inductance, while securing balanced voperation of said circuits from a position above the nodal point: in. said inductance.

2. Ina high -power amplification system for high frequency currents, a plurality of stages of amplification.each constituted by electron tubes, means coupling the output circuit of one electrontubewith the ,input' circuit .ofthe succeeding electron tube comprising an inductance and a pair ofrvariable condensers :diSposed in series, said condensers being simultaneously adjustable for 10- cating'and positioning a node offthe output voltage intermediate the ends of said inductance, a connection common to eachof said variable condensers between said variable.

condensers to the grid electrode of the sueceeding electron tube, abalanced circuit connected with theJoutputcircuit of the succeeding electron tube and a point in vsaid inductance above-the node, saidvariable condensersbeing simultaneously adjustable for locating and positioningthe nodal point in said inductance for effecting, grid excitation of the succeeding electron tube from a point 7 in. said inductance below said nodal point,

whilst-securing;balanced operation of said circuits from a point above'the nodal point 'insaidlinductance. j p

3. 'An amplification system comprising a pluralityrof electron tubes each having grid,

filament. and plate circuits, the output circuit ofnoneelectron-tube having, two par allel branches, one of said branches comprisinga capacity and the other branch com-J prising .an' inductance andcapacity in series,

said-lastnamedlcapacity providing a nodal pointuofj voltage intermediate the ends=of said inductance, a connection from said inductance on one side =of said nodal point to the grid of a succeeding. electron tube and a connection from said inductanceon the opposite side vof said l nodal point through; a .a

capacity t to therplate circuit of said succeed; ing electron tube. 7

Anl amplification. system comprising. a

plurality; of electrontub'es each having grid,

filament and (plated circuits, r the output circuit one; electron tube having two parallell-branches, one ofsaidebranches 00111-1 prising a variable capacity and the other branch comprising a variable inductance and a variable capacity in series, said last named capacity providing a nodal point of voltage intermediate the ends of said inductance, a connection from said inductance on one side of said nodal point to the grid of a succeeding electron tube and a connection from said inductance on the opposite side of said nodal point through a Variable capacity to the plate circuit of said succeeding electron tube, whereby said last named capacity stabilizes said circuits.

ALBERT H. TAYLOR. 

